Methylation with sodium naphthalenide for the analysis of substituent distribution of trimethylsilyl celluloses and their evaluation

The substitution pattern of trimethylsilyl celluloses silylated withhexamethyldisilazane and N,N-dibutylamino­trimethylsilane was determined bymethylation analysis. Methylation with sodium hydride/methyl iodide wasaccompanied by significant desilylation because sodium hydride is alwayscontaminated with sodium hydroxide. Sodium naphthalenide prepared in tetrahydrofuran under anhydrous reaction conditions alloweda reduction of the extent of desilylation to less than 10 percent. In allcases preferred silylation of the 6-position was found. Celluloses silylatedwith hexamethyldisilazane and N,N-dibutylaminotrimethylsilane had almostidentical substituent distributions. Lower reaction temperature resulted inhigher regioselectivity.